1. Field of the Invention
The present invention concerns a waveguide antenna assembly for a magnetic resonance tomography apparatus.
2. Description of the Prior Art
Magnetic resonance apparatuses, in particular for the examination of patients via magnetic resonance tomography, are generally known (for example from DE10314215B4)
Modern magnetic resonance systems (also called MRI or MRT) normally operate with multiple different antennas to emit radio-frequency pulses for nuclear magnetic resonance excitation and/or to receive induced magnetic resonance signals. A magnetic resonance system frequently has a larger coil (known as a whole-body coil, also called a body coil) that is normally permanently installed in the apparatus, as well as multiple small surface coils (also called local coils). In contrast to a whole-body coil, surface coils serve to acquire detailed images of body parts or organs of a patient that are located relatively close to the surface of the body.
It is known from Pruessmann et al that an antenna for UHF-MRI is based on the principle of wave propagation in waveguides. Use is made of the fact that a metal tube as already present is in an MR system (for example as a standard provided RF shield or an inner metal wall of the magnet) can function as a waveguide up to a specific limit frequency. This limit frequency can be exceeded in MRT systems.